Antenna



FIG. 1 is a perspective view of an antenna showing my new design in use;

FIG. 2 is another perspective view of the antenna showing my new design;

FIG. 3 is a front view thereof; and,

FIG. 4 is a side view thereof, the opposite side view being a mirror image thereof.

The broken lines illustrate environment only and form no part of the claimed design. 

The ornamental design for an antenna, as shown and described. 